1. Field of Invention
This invention relates to a process for the production of polybenzimidazole filaments and fibers. More particularly, the invention relates to the production of moldable polybenzimidazole filaments and fibers.
2. Prior Art
Polybenzimidazole is a non-flammable polymer which may be formed into textile fibers having outstanding thermal, physical, and chemical stability. Processing parameters are well established for the extrusion of polybenzimidazole solutions into fibrous materials. Generally, polybenzimidazole fibers are produced by either dry or wet spinning. However, the prior art processes for the production of polybenzimidazole fibers do not produce products which are subsequently moldable. Usually, the prior art processes for preparing polybenzimidazole fibers include a washing step to remove the residual solvent in the fiber.
Commonly assigned U.S. Pat. No. 3,541,199 discloses a process for rendering polybenzimidazole fibers non-foamable so that they can be hot drawn without foaming or exploding. The patent states that sometimes after residual spinning solvent is removed by washing, polybenzimidazole fibers will explode or foam while being hot drawn. However, since according to the patent the residual solvent is removed from the fibers, the fibers are not readily moldable and, therefore, will not produce homogeneous composite articles.
In commonly assigned U.S. Pat. No. 4,598,099, a process for the production of polybenzimidazole foams is disclosed. The patent discloses that articles, such as fibers, can be prepared and foamed. However, the process requires the removal of residual solvent before foaming.
U.S. Pat. No. 4,092,274 discloses foamed, cross-liked polybenzimidazoles. However, the patent does not disclose the preparation of fibers that are moldable and can be foamed.
U.S. Pat. No. 4,263,245 discloses a process for producing high strength, ultra-low denier polybenzimidazole filaments. However, a washing step is included in which the polybenzimidazole solvent within the fiber is essentially removed so that less than about one percent by weight of the solvent is left in the final filament. The filaments produced by the process of this patent are not readily molded.
Accordingly, it is an object of the present invention to provide an improved process for the production of polybenzimidazole filaments.
It is also an object of the present invention to provide a commercially practical process for the production of polybenzimidazole filaments without diminution of the fiber's desired tensile properties.
It is a further object of the present invention to provide a process for the production of moldable polybenzimidazole filaments.
It is another object of this invention to produce polybenzimidazole based foams.
These and other objectives are obtained by preparing polybenzimidazole fibers according to the process of the instant invention.